Nd含量对纳米晶Nd_xFe_(94-x)B_6合金磁性能的影响  

EFFECTS OF Nd CONTENT ON MAGNETIC PROPERTIES OF NANOCRYSTALLINE Nd_xFe_(94-x)B_6 ALLOYS

作　　者：包小倩[1] 高学绪[1] 朱洁[1] 张茂才[1] 周寿增[1] 

机构地区：[1]北京科技大学新金属材料国家重点实验室,北京100083

出　　处：《金属学报》2009年第8期988-993,共6页Acta Metallurgica Sinica

摘　　要：用X射线衍射(XRD)、差示扫描量热分析(DSC)、高分辨扫描电镜(HRSEM)和振动样品磁强计(VSM)等研究了Nd含量对快淬纳米晶Nd_xFe_(94-x)B_6(x=11.0—16.8)合金的组织结构、磁性能、交换耦合作用和矫顽力的影响.结果表明,22 m/s(甩带速度)快淬带在最佳退火条件下,合金带的内禀矫顽力H_(ci)由x=11.0的601.3 kA/m单调升高到x=16.8的1277.3 kA/m;相反,剩余磁极化强度J_r由x=11.0的1.047 T单调下降到x=16.8的0.721T,最大磁能积(BH)_(max)随Nd含量增加先升高后下降;Nd_(11.8) Fe_(82.2)B_6合金带的综合性能最好:J_r=0.992 T,H_(ci)=727.9 kA/m,(BH)_(max)= 137.2 kJ/m^3.Nd_2Fe_(14)B晶粒之间的交换耦合作用随Nd含量增加而降低,但x=16.8的合金带仍具有较强的交换耦合作用矫顽力主要由钉扎场决定.最佳退火后,合金薄带的晶粒尺寸随Nd含量增加无明显变化.针对不同Nd含量的合金,建立了一个组织模型,利用该模型很好地解释了Nd含量对磁性能及交换耦合作用的影响机制.Nanocomposite magnets have attracted considerable attention as a probable new generation of permanent magnets with a potential theoretical maximum energy product of 1 MJ/m3 due to remanence enhancement resulting from intergrain exchange interactions between magnetically soft and hard grains. However, the presence of soft phase increases remanence but coercive field is significantly decreased. Alloys with Nd content higher than 11%（atom fraction）, i.e., close to the stoichiometry composition of Nd2Fe14B, are being studied to further improve coercivity. Nanocrystalline NdxFe94-xB6（x=11.0 16.8） alloys were prepared by melt-spinning at a rate of 22 m/s cooperating with subsequent annealing. The effects of Nd content on microstructure, magnetic properties, exchange coupling interactions and coercivity mechanism have been studied by X-ray diffraction （XRD）, differen- tial scanning calorimeter （DSC）, high resolution scanning electron microscope （HRSEM） and vibrating sample magnetometer （VSM）. The intrinsic coercivity Hci increases from 601.3 kA/m for x=11.0 to 1277.3 kA/m for x=16.8 monotonously, and on the contrary, the remanent polarization Jr reduces from 1.047 T for x=11.0 to 0.721 T for x=16.8. The maximum energy product （BH）max first increases and then reduces with increasing Nd content. The optimum magnetic properties with Jr=0.992 T, Hci=727.9 kA/m and （BH）max=137.2 kJ/m3 are achieved by annealing melt-spun Ndll.sFes2.2B6 ribbons. Although the exchange coupling interactions are degraded by increasing Nd content in the ribbons, it is still relatively strong for the alloy with x=16.8. The coercivities of alloys are determined mainly by pinning field. Nd content almost does not influence microstructure under optimal annealing conditions. The microstructral model of nanocrystalline Nd-Fe-B with different Nd content is presented and used to analyze the effect of Nd content on magnetic properties and exchange coupling effect well.

关 键 词：纳米晶Nd-Fe-B 交换耦合作用 矫顽力机制 显微组织 

分 类 号：TG132.2[一般工业技术—材料科学与工程]